A variety of optical devices employ optical attenuators to reduce the intensity of light signals carried within the optical device. These optical devices can employ ridge waveguides to confine light signals to particular regions of the optical device. A ridge waveguide is generally defined by a ridge of a light transmitting medium extending upward from slab regions of the light-transmitting medium.
Attenuators used in conjunction with ridge waveguides often employ free carrier absorption to achieve attenuation. During operation of these attenuators, electrical energy is applied to doped region of the light-transmitting medium so as to inject free carriers into the waveguide.
The doped regions are generally positioned in trenches positioned on opposing sides of the ridge waveguide. These trenches extend part way into the slab regions. As a result, light-transmitting medium is positioned in the bottom of each trench. The doped regions are formed in the light-transmitting medium at the bottom of the trenches.
The inventors have found that fabricating these attenuator structure results in an undesirably low yield of product. For instance, a large percentage of the devices have attenuators with undesirably low performance levels and are accordingly treated as waste. As a result, there is a need for an attenuator structure associated with a higher fabrication yield.